The proposed research concerns cell motility which is integral to a variety of processes including normal growth and development, wound healing, inflammation and neoplasia. A fundamental understanding of the basis of cell motility should lead to the development of clinically useful modulators of this process. The crawling behavior of most cell types is dependent upon the actin cytoskeleton and its associated proteins. Gelsolin has regulated actin filament nucleating, capping, and severing activity, and evidence suggests that it plays a fundamental role in cell motility. However, transgenic mice completely deficient in gelsolin are viable under laboratory culture conditions. This suggests that other proteins exist which can fulfill a similar role in cell motility. One possible candidate is the protein produced by the flightless-1 gene which has recently been cloned and found to share sequence homology with gelsolin. The objective of this research proposal is to examine the structure and function of the flightless-1 protein. After cloning the mouse gene for the protein, its mRNA expression in various tissues will be investigated. The full length protein and deletion mutants will be expressed in a bacterial system and studied using standard biochemical techniques as well as specialized methods for analysis of its interaction with actin. Antibodies against the protein will also be prepared for use in screening tissues and embryonic stages as well as in purification. Transgenic animals will be developed to studs the effect of deletion of the protein on the developing and mature animal. If viable, transgenic animals with deletions of both gelsolin and the flightless-1 protein will be generated and characterized.